1. Field
The present disclosure relates to a semiconductor phosphor nanoparticle and a light-emitting device that includes the semiconductor phosphor nanoparticle and specifically to a semiconductor phosphor nanoparticle that has a protected surface and a light-emitting device that includes such a semiconductor phosphor nanoparticle.
2. Description of the Related Art
It is known that a quantum size effect is observed when the size of semiconductor nanoparticles is as small as an exciton Bohr radius. A quantum size effect refers to a phenomenon in which, when the size of a substance is reduced, electrons in the substance cannot freely move and cannot have arbitrary energy but a specific energy. It is also known that a change in the size of semiconductor nanoparticles in which electrons are confined causes a change in the energy state of the electrons, that is, the smaller the size of semiconductor nanoparticles, the shorter the wavelength of the light emitted from the semiconductor nanoparticles. The application of semiconductor nanoparticles, which exhibit the quantum size effect described above, as phosphors has been focused on and studied.
Since semiconductor nanoparticles that exhibit a quantum size effect have a small particle size, the specific surface area of the semiconductor nanoparticles is large. Therefore, surface defects of semiconductor nanoparticles greatly affect the luminescence intensity of a phosphor. Furthermore, if the surfaces of semiconductor nanoparticles are subjected to oxidation or the like, the overall chemical stability of the semiconductor nanoparticles may be impaired.
In order to enhance the chemical stability of semiconductor nanoparticles and to achieve high luminescence intensity, for example, there has been proposed a technique in which a coating layer is formed on the surface of semiconductor nanoparticle.
International Publication No. WO2009/028282 discloses a luminescent material having increased luminous efficiency, a narrowed luminescent spectral band width, and enhanced chemical durability, which is produced by, in a surface treatment of semiconductor nanoparticles capable of emitting light, reducing the insufficiency of the surface conditions of the semiconductor nanoparticles which is due to a mismatch in lattice constants or steric hindrance, which has been unavoidably caused in the related art. Specifically, a luminescent material that includes semiconductor nanoparticles having an average particle diameter of 2 nanometers or more and 12 nanometers or less and a band gap of 3.8 electron-volts or less, the semiconductor nanoparticles each being coated with a layer including silicon, is disclosed. The peak luminous wavelength of the semiconductor nanoparticles included in the luminescent material is 20 nanometers or more greater than the peak luminous wavelength of the semiconductor nanoparticles when not included in the luminescent material.